Plug your Apple Pencil into the Lightning connector on your iPad. You can also charge with a USB Power Adapter by using the Apple Pencil Charging Adapter.
Apple Pencil will fast charge when plugged into either power source.
To see how much charge your Apple Pencil has left while you're using it, check the Today View on your iPad. Just swipe from left to right on the Home screen or Lock screen. To see how much charge your Apple Pencil has left, check the Batteries widget.